Muscle contraction headache (MCH) is one of the most common psychosomatic disorders, with estimates of incidence in the general population ranging from 20% to 60%. Although the disorder is usually not considered serious, MCH accounts for a high number of patient contacts by physicians, and it exacts a high cost to society in terms of personal distress and limitations on occupational, recreational , and social activities. Ironically, there is no acceptable operational definition of MCH that is based on myogenic hyperactivity, which is presumed to play a key role in the pathophysiology. Instead, a diagnosis of MCH is usually based on the exclusion of organic and vascular etiologies and on the patients' subjective report for the type of pain experienced. Nonetheless, many medical and behavioral treatments are aimed at reducing tension levels in key head and neck muscles. The long-term objective of the proposed research is the development of an operational definition of MCH that takes into account the relation between measured muscular activity and pain. The development of such a definition would be expected to lead to improved diagnostic and treatment techniques. The following three specific aims of the proposed research are related to the achievement of the long term objective: (1) examine the test- retest reliability of a psychophysiological test battery designed to measure the activity of key head and neck muscles of MCH patients and normal controls under standardized laboratory conditions, (2) compare the behavior of key head and neck muscles of MCH patients and normal controls in the laboratory and in their natural environment, (3) define the temporal and topographic relationships of MCH episodes with their emotional, behavioral, and physiological antecedents and consequences through ambulatory monitoring in the natural environment. In laboratory studies, MCH and control subjects will perform choice reaction time, psychomotor tracking, and cold pressor tests while EMG activity in head and neck muscles is recorded. The test- retest reliability, validity, and sensitivity of these tests will be evaluated. In the natural environment data will be obtained using an ambulatory EMG recorder that is capable of measuring EMG activity over a 24-hour period. Subjects will also periodically rate their perceived pain and stress levels, and they will describe their ongoing behavior. These data will be related to EMG data over periods of time ranging from minutes to days.